GI drugs

Question 1

Antacids Drugs

Answer 1

e.g. calcium carbonate

Brands Drugs: Gavison, Peptac.

Question 2

MoA of Antacids

Answer 2

Neutralises stomach acid + acting as a buffer. Raises Stomach pH.

Used for GORD, Peptic ulcers, Dyspepsia

Question 3

Anti-diarrhoeal (Bulk-Formation).

Answer 3

E.g. Ipsabgol Husk

Absorbing water in the intestines, which thickens the stool and slows its passage through the bowels.
For: Acute cholecystitis, Eradication of H.pylori, Acute pancreatitis

Question 4

Antidiarrhoeal / anti-mobility

Answer 4

e.g. loperamide, codeine phasphate (used for pain)

Question 5

MoA of Antidiarrhoeal / anti-mobility

Answer 5

Agonist activity at opioid resceptors via ENS = blocks Ach release decreasing peristalsis.

For: acute diarrhoea, IBS
NO USE for UC + c. diff

Question 6

H2 A

Answer 6

Ranitidine
Receptor located on basolateral membrane of parietal cells = BLOCKS THAT RECEPTOR.

FOR: PU (DU/GU)

Question 7

Laxatives (Stimulants)

Answer 7

Senna, Na picosulfate, bisocodyl, glycerol suppository.

For… Given to patients who are on opioids and experience constipation/faecal impaction, following Abdominal surgery.

Question 8

MoA of Laxaitves (stimulants)

Answer 8

Increases frequency of bowel movements via stimulating electrolytes, H2O + Parasympathetic NS.

Question 9

Laxatives (bulk-forming):

Answer 9

e.g. Ispagula Husk, methylcellulose.

For… Constipation + faecal impaction, mild -chronic diarrhoea associated with diverticular / IBS.

Question 10

MoA of Laxatives (bulk-forming):

Answer 10

Improve on stool consistency + volume to prove bowel movement via osmosis H2O are attracted to stool, increasing bulk + stimulate peristalsis.

Question 11

Laxative (Osmotic)

Answer 11

e.g. lactulose, macrogols + phosphate enemas (but try Lax stimulant before this)

For… constipation + faecal impaction, bowel preparation before endoscopy / surgery + hepatic encephalopathy

Question 12

MoA of Laxative (Osmotic)

Answer 12

osmosis attracted to stool = increasing bulk + stimulates peristalsis. Keeps H2O in bowel to increase the volume of faeces.

Question 13

PPI

Answer 13

e.g. omeprazole (taken in morning 30mins - 1hr before eating.

For… GORD, dyspepsia, Peptic ulcers (can be H. pylori).

Question 14

MoA of PPIs

Answer 14

Irreversibly blocks H/ATPase at apical membrane (proton pump) - inhibiting gastric acid.

For long-term use it tends to increase the effects of warfarin.

Question 15

Anti-muscarinic:

Answer 15

e.g. Hyoscine butylbromide

For… To relieve SM spasm in IBS. Can be used as motion sickness drug e.g. atropine, LAMA + SAMA .

Question 16

MoA of Anti-muscarinic:

Answer 16

Competitive antagonist acetylcholine receptor = blocks parasympathetic division. Reduces spasm of SM peristalsis + glandular secretion via blocking M3.

Question 17

Amino salicylates

Answer 17

e.g. mesalazine, balsalazide, sulfasalazine (used for RA)

For… these are the 1st line treatment for UC.

Question 18

MoA of amino Salicylates

Answer 18

5-ASA exerts anti-inflammatory + immunosupressant effect

Contraindication = PPIs

Question 19

Antiemetics (D2R)

Answer 19

e.g. Domperidone + Metoclopramide (IV/IM)

Fo… Nausea + vomiting in wide range of conditions.

• used in drug/chemo-induced nausea + vomiting
• GORD + other GI conditions = as a add on in patients who don’t respond to PPIs + H2 receptor blockers.

Question 20

MoA of Antiemetics (D2R)

Answer 20

Blocks D2 receptors (expressed at chemoreceptor trigger zone) lies outside of BBB (important in detecting toxins such as opiates). At high dose, blocking 5-HT3 receptor may contribute to antiemetics effect.

Question 21

Antiemetics (H2R)

Answer 21

e.g. cyclizine, cinnarazine, promethazine.

For… Nausea + vomiting = mostly motion sickness + vertigo (dizziness + effect of balance), post-operative N+V.

Question 22

MoA of Antiemetics (H2R)

Answer 22

Blocks H1 receptor in vomiting centre + causes sedatives effects.

*Blocks M1 (Ach receptor in the vestibular apparatus.

Question 23

Antiemetics (phenathiazines)

Answer 23

e.g. Procloperazine, cholorpromazine

For… N+V in a wide range of conditions, vertigo + sometimes chemo-induced N+V.

*Psychiatric disorder e.g. schizophrenia.

Question 24

MoA of Antiemetics (phenathiazines)

Answer 24

Competitively blocking D2, H1 + M1 receptors in vomiting centre, vestibular system + peripherally in GUT.

Question 25

Antiemetics (5-HT Receptors)

Answer 25

e.g. Ondansetron, granisetron, palonosetron

For… N+V associated with chemo-induced + radiotherapy, surgery involving the use of anaesthetic agent (PONV).

*EMs for hyperemesis gravidarum (sickness in pregnant women).

Question 26

MoA of 5-HT Receptors:

Answer 26

Blocks inotropic 5-HT3 Receptors. Located in CTZ, Nucleus tractus solitaries + peripherally. CTZ senses emetogenic stimuli present in blood, where 5-HT released from enterchomaffin cells in gut stimulate vagal afferent via the NTS = activating vomiting centre

Question 27

Antacids side effects

Answer 27

contains Na + K. should be used wisely in patients with restrictive salt intake e.g. hyperkalemia + renal impairment.

Question 28

Antidioarrhoel side effects

Answer 28

Prolonged use can cause constipation + cramps.

DO NOT USE on acute UC (risk of megacolon + perforation), acute bloody diarrhoea (dysentery) + c.diff colitis

Question 29

H2 Antagonist side effects

Answer 29

Only HELPS with symptoms. Given to patients who cannot tolerate PPIs.

Diarrhoea, headaches, abdo pain + dizziness.

Cimetidine (anti-androgenic) blocking testosterone = gynaecomastia.

Question 30

Laxatives (stimulants) side effects

Answer 30

Abdo pain, cramping, diarrhoea. Prolonged use: irreversible atonic colon + reversible melanosis coli.

Question 31

Laxatives (bulk-forming) side effects

Answer 31

Distension + flatulence. Faecal impaction + obstruction.

Question 32

Laxative (osmotic) side effects

Answer 32

Cramps, nausea, flatulence, possible diarrhoea.

Question 33

PPIs side effect

Answer 33

Diarrhoea, headaches, abdo pain, nausea, fatigue, dizziness is common. Prone to c. diff after long-term use.

Question 34

Anti-muscarinic side effect

Answer 34

Due to suppressed ANS: tachycardia, dry mouth, constipation, urinary retention, blurred vision.
Be aware of patient with cardiac arrhythmia + glaucoma.

Question 35

Amino salicylates side effects

Answer 35

• Mesalazine = Upsets + headaches and possibly renal impairment.
• Sulfasalazine = hypersensitivity reaction can effect UC patients adversely.

PPIs can cause breakdown of Mesalazine.

Question 36

Antiemetics (D2 receptors) side effect

Answer 36

Diarrhoea (common)

• Metoclopramide = causes extrapyramidal syndromes (movement disorders – common in children + young adults), motor restlessness, spasmodic torticollis + oculogyric (involuntary upper gaze of the eyes).
• Domperidone = less adverse effects.

Question 37

Antiemetics (H2 receptors) side effects

Answer 37

Drowsiness + sedation.

• Cyclizine is least likely to cause sedation (avoid motor tasks).
• Dry mouth, transient tachycardia (IV administration).

AVOID patients with hepatic encephalopathy/prostatic hyperplasia (anti-muscarinic increases likelihood of urinary obstruction).

Question 38

Antiemetics (phenathiazines) side effect

Answer 38

Drowsiness + postural hypotension (common).

• Extrapyramidal symptoms (due to D2 block)
• long-term = tardive dyskinesia/Parkinson’s, long QT interval

AVOID liver disease

Question 39

Antiemetics (5-HT Receptors)

Answer 39

Severe/prolonged constipation, intestinal obstruction, stricture, toxic megacolon, ischemic colitis, Crohn’s disease, diverticulitis. Prolonged QT (if HIGH dose is given).

SE: constipation, diarrhoea + headaches